Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$191.55	4.341%	$199.8652	$199.87	$199.85	$199.90
Purchase #2	$221.88	5.832%	$234.82	$234.82	$234.80	$234.80
Purchase #3	$231.43	12.271%	$259.8288	$259.83	$259.85	$259.80
Purchase #4	$156.97	3.218%	$162.0213	$162.02	$162.00	$162.00
Purchase #5	$100.80	9.129%	$110.002	$110.00	$110.00	$110.00
Purchase #6	$174.89	11.784%	$195.499	$195.50	$195.50	$195.50
Purchase #7	$69.81	12.606%	$78.6102	$78.61	$78.60	$78.60
7 purchase totals =	$1,147.33		$1,240.6465	$1,240.65	$1,240.60	$1,240.60